Gear pump with seal plates

ABSTRACT

A high pressure rotary gear pump including a housing having a pair of external gear members intermeshing at a location between an inlet and an outlet, a pair of shafts carrying the gear members and having opposite ends mounted in bearings in the housing, a pair of thin generally 8-shaped floating seal plates around the shafts at opposite sides of the gears, means providing a definite primary area on the gear side of each plate subjected to outlet pressure applying a primary force tending to separate the plate from the gears, means defining a pressure balance area subjected to outlet pressure to overcome the primary force, a recess in the periphery of each plate at each end thereof supplying outlet pressure to the primary pressure balance area, means defining secondary areas between the inlet and the primary areas on the gear side of each plate subjected to pressure gradients varying with speed and applying secondary forces tending to separate the plate from the gears, means defining a pressure balance area on the remote side of each plate opposed to each secondary area, an aperture in each plate intermediate the ends of each secondary area communicating the secondary area with the opposed pressure balance area to overcome the secondary force, and a land on the periphery of each plate between the inlet and each peripheral recess beveled to deform in use on contact with the housing when subjected to high pressure, thereby to provide an effective seal between the inlet and each recess.

United States Patent Pollman et al.

[ 1 Jan. 30, 1973 [541 GEAR PUMP WITH SEAL PLATES {75] Inventors:Frederic W. Pollman; Lee R. Frandsen; Charles D. Throckmorton, Sr.,

all of Rockford, Ill.

[73] Assignee: Sundstrand Corporation [22] Filed: Jan. 27,1971

[21] Appl. No.: 110,178

[52] U.S.Cl ..418/71 [51] lnt.Cl. ..F0lc 21/00 [58] Field of Search ..41 8/7 l-74 [56] References Cited UNITED STATES PATENTS 3,213,799 10/1965Trick ..418/74 3,053,192 9/1962 Nonnenmacher 418/73 3,285,188 11/1966Kita ..418/74 Primary ExaminerC. J. Husar AttorneyHofgren, Wegner,Allen, Stellman & Mc- Cord [57] ABSTRACT A high pressure rotary gearpump including a housing having a pair of external gear membersintermeshing at a location between an inlet and an outlet, a pair ofshafts carrying the gear members and having opposite ends mounted inbearings in the housing, a pair of thin generally 8-shaped floating sealplates around the shafts at opposite sides of the gears, means providinga definite primary area on the gear side of each plate subjected tooutlet pressure applying a primary force tending to separate the platefrom the gears, means defining a pressure balance area subjected tooutlet pressure to overcome the primary force, a recess in the peripheryof each plate at each end thereof supplying outlet pressure to theprimary pressure balance area, means defining secondary areas betweenthe inlet and the primary areas on the gear side of each plate subjectedto pressure gradients varying with speed and applying secondary forcestending to separate the plate from the gears, means defining a pressurebalance area on the remote side of each plate opposed to each secondaryarea, an aperture in each plate intermediate the ends of each secondaryarea communicating the secondary area with the opposed pressure balancearea to overcome the secondary force, and a land on the periphery ofeach plate between the inlet and each peripheral recess beveled todeform in use on contact with the housing when subjected to highpressure, thereby to provide an effective seal between the inlet andeach recess.

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PATENIED JAN 30 I975 SHEET 2 BF 4 PAIENTEUJAN30 ma 3.713.759

SHEET u UF 4 3500EPM 2500RPM 90 VOL UMET/P/c 1500 RPM [FHC/ENC) 801000RPM (1%) 500PPM 70 60 I l l 90 OVFIEA! L 35 00 PPM EFF'lC/F/VC Y2500 P K 80 1500 PM 1000RPM- 10'00 zo oo 3000 I b/SCAWPGEP/PESSU/Ff/RSI) GEAR PUMP WITH SEAL PLATES BACKGROUND OF THE INVENTIONThe present invention relates to rotary gear pumps including a pair ofexternal gear members with intermeshing teeth, and in the preferredconstruction illustrated herein the gear members are supported by meansof a pair of parallel shafts having the gear members fixed thereon andhaving opposite ends extending from the gear members into bearings in ahousing mounting the shafts for rotation. The housing is formed with apair of generally cylindrical gear cavities intersecting centrally ofthe housing and providing a generally 8-shaped configuration. An inletis provided at one side of the intermeshing teeth and an outlet isprovided at the other side of the intermeshing teeth. The ends of theteeth at the periphery of the gears in rotating from the inlet to theoutlet are closely adjacent the surrounding housing. Seal plates engagethe sides of the gears.

In the past, it has been customary to provide one or more plates at oneor both sides of the gears mounted for movement axially relative to thegears into sealing engagement with the sides of the gear teeth. Ingeneral, there have been three types of construction involving movableseal plates of the character mentioned, together with provision forsupply of fluid under pressure to the remote side of such plates to urgethe latter toward the sides of the gear teeth. One type has involved athin flexible plate clamped at the periphery between housing memberssuch as the center spacer member and an end cover member. In a secondtype, the side plates are in the form of individual bearing blocks foreach shaft end of substantial thickness and mounted for movement towardthe gears. In a third type there are plates of substantial thicknessapparently intended to be rigid in use and floating in the sense thatthey are not clamped at the periphery but free to move axially.

Generally, each of the prior constructions is subject to somedisadvantages. In the first mentioned construction involving one or morethin flexible plates clamped at the periphery, the remote side of theplate is often compartmented for application of pressures correspondingsomewhat to pressures in the gear cavity. However, it appears that oneor more areas at the remote side of the flexible plate is subjected torelatively high pressure, such as outlet pressure, greatly in excess ofthe pressure at the gear side of the plate, result ing in extremely highlocalized loads with accompanying heat and wear creating large torquelosses. Further, the periphery of the flexible plate is usually clampedwith some axial clearance from the gears, creating a leak path aroundthe gears which is difficult to control. Thus, while the thin flexibleplate is relatively inexpensive to manufacture, it is difficult toprovide high efficiency levels in such constructions.

In the second and third constructions utilizing thick bearing blocks orside plates, the blocks or plates are not usually flexible and are oftensubjected to full discharge pressure intended to force the blocks orplates against the side of the gear teeth. Since the blocks or platesare not flexible, the force distribution on the remote side is generallynot related to the force on the gear side tending to separate the platefrom the gear. As a result, the blocks or plates often tilt and bind dueto severe pressure imbalance and result in leakage due to the tilting.The unbalance and tilting loads can be quite high, causing high torquelosses and subsequent wear. By changing the pressure loading pattern tomore nearly match the blowoff forces, some of the performancedeficiencies can be overcome to provide higher efficiencies, butproduction of the components requires close manufacturing tolerances andthe product is expensive as well as bulky.

SUMMARY OF THE INVENTION In the present invention, a thin floating plateis utilized at each side of the gears and is held in sealing contactwith the sides of the gear teeth by a sealing force which isproportioned according to the blowoff force for all areas and for alloperating conditions. Force levels are determined for each of separatesectors around the periphery of the gear in a manner to provide acomplete force topography over the entire surface of the pressurebalance plates at all conditions of speed and pressure, so thatcounterbalance forces may be accurately applied. The system providesbetter sealing with reduced mechanical and fluid losses and therebycreates high efficiencies with near zero fluid leakage and near zerotorque losses.

In the preferred form, each pressure balance plate has a generally8-shaped configuration adapted to fit on both shafts against one side ofboth gears. Provision is made for subjecting a definite primary area atthe gear side of the plate to outlet pressure, so that a definite areaon the remote side of the plate may be subjected to counterbalanceforces overcoming the tendency of the primary force to separate theplate from the gears. The primary area extends from the outlet chamberaround the gears more than half way toward the inlet chamber. Secondaryareas at the gear side of each plate extend from the inlet around thegears to the primary areas. The secondary areas are subjected to apressure gradient with pressure increasing from substantially zero atthe inlet to substantially outlet pressure at the juncture of thesecondary area with the primary area. Pressure at intermediate value isapplied to the remote side of the plate to oppose the secondary forcetending to separate the plate from the gears. While the plate may bethin enough to flex, the blowoff forces are carefully opposed as aresult of which there is substantially no deformation of the plate andno localized wear or friction and also no tilting resulting in leakage.

Preferably the plate has a recess on the periphery at each end forclearly defining the primary area and for supplying fluid to thepressure balance area opposing the primary blowoff force. A land isprovided on the periphery of each plate between the inlet and eachrecess, and the land is beveled to deform against the housing when theplate is put into use and subjected to high pressure. The deformationenables the land to conform precisely to the surrounding housing andprovides excellent sealing between the inlet and the adjacent peripheralrecess on the plate.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional viewthrough a pump embodying the present invention, taken at about the line11 of FIG. 2;

FIG. 2 is a cross-sectional view taken at about the line 2-2 of FIG. 1;

FIG. 3 is an elevational view of a pressure balance seal plate taken atabout the line 3-3 of FIG. 1, viewing the pressure balance plate fromthe side in contact with the gears;

FIG. 4 is an elevational view of the pressure balance plate taken atabout the line 4-4 of FIG. 1 viewing the opposite side of the plate;

FIG. 5 is a cross section taken through the seal plate at about the line5-5 of FIG. 4;

' FIG. 6 is a cross-sectional view taken at about the line 6-6 of FIG. 1viewing the inner surfaceof the end housing member;

FIG. 7 is a sectional view through the housing member taken at about theline 7-7 of FIG. 6 showing the inlet and outlet ports in the housingmember;

FIG. 8 is a fragmentary enlarged and exaggerated sectional view taken atabout the line 88 in FIG. 4, but showing the relationship of the platerelative to the surrounding housing after deformation in use.

FIG. 9 is a pressure diagram illustrating a relatively gradual pressuregradient from inlet pressure to outlet pressure with a pump operated atlow speed;

FIG. 10 is a pressure diagram illustrating a relatively steep pressuregradient from inlet pressure to outlet pressure with a pump operated atrelatively high speed.

FIG. 11 is a diagram illustrating pressure distribution on the gear sideof the seal plate tending to separate the plate from the gears.

FIG. 12 is a diagram illustrating pressure variation at the gear side ofthe pressure plate in a predetermined sector having a lengthapproximately equal to the pitch of one tooth and subjected to outletpressure.

FIG. 13 is a diagram illustrating the application of pressure balancingforces.

FIG. 14 is a graph illustrating volumetric efficiencies of the presentpump at various discharge pressures and speeds; and

FIG. 15 is a graph illustrating overall efficiencies in the present pumpat various discharge pressures and speeds.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings inmore detail, a pump construction embodying the present invention isillustrated as including a housing comprised of three outer membersincluding an end housing member 10 suitably constructed for mounting thepump upon an appropriate support, an end housing member 11 formed withan inlet and an outlet, and a central housing member 12 in the form of aspacer plate. The housing members 10, 11 and 12 are suitably aligned asby pins 14 at the top and bottom of FIGS. 1 and 2, and held in assembledrelationship by machine bolts as at 16. The housing members define aninterior cavity for the pump gears, sealing means and inlet and outletchambers.

Drive gear 18 is formed on a drive shaft 19, and idler gear or drivengear 20 is formed on a driven shaft 21. The shafts l9 and 21 arearranged on parallel spaced axes in the housing with the teeth on thegear members meshing at a zone centrally located in the housing cavity.Opposite ends of the shaft 21 project into bore recesses 24 and 25 inthe housing members 11 and 10. The bore 24 ends in the housing member 11and the recess 25 in the housing member 10 is closed by an appropriateseal 26. Opposite ends of the shaft 19 project into bore recesses 28 and29 in the housing members 11 and 10. The bore 28 ends in the housingmember 11 and the recess 29 in the housing member 10 is closed by anappropriate seal means 30 including provision for a projecting endportion 32 on shaft 19 adapted to be connected with a suitable primemover. Opposite end portions of the drive shaft and driven shaft aremounted in similar bearing sleeves 34 fixed in the housing recesses. Inorder to provide for lubrication, the interior surface of each bearingsleeve 34 includes a longitudinal groove 35 preferably located as shownin FIG. 6.

As seen in FIG. 2, an inlet chamber 37 is provided in the spacer plate12 at one side of the zone of intermeshing gear teeth and an outletchamber 38 is provided in the spacer plate 12 at the other side of thezone of intermeshing teeth. Both chambers extend outwardly from thespacer plate partially into the end housing members. The inlet chamber37 is always sealed from the outlet chamber 38 by means of tooth contactin the zone of intermeshing teeth and by sealing means engaging theouter edges of the gear teeth. While the seal between the inlet chamberand the outlet chamber provided by tooth contact at the zone ofintermeshing teeth is constantly changing along the line of actiontangent to the base circles of the gears during rotation of the gears,the inlet chamber is generally defined at one side of the intermeshingteeth and the outlet chamber is generally defined at the other side ofthe in termeshing teeth. The outer tips of the gear teeth rotating frominlet to outlet contact inner surfaces of the spacer plate 12 as at 40and 41 which define generally cylindrical gear cavities intersecting atthe zone of intermeshing teeth. The sides of the gear teeth are sealedby means of pressure balanced seal plates 43 and 44 generally of8-shaped configuration fitted around the shafts and against oppositesides of the gears in cavities 40 and 41 in the spacer plate.

The inlet chamber 37 communicates with an axially disposed inlet passage48 FIGS. 6 and 7 in the end housing member 11 having a laterallydirected internally threaded terminus, and outlet chamber 38communicates with an axially disposed outlet passage 49 in the endhousing member 11 having a laterally directed internally threadedterminus. If desired, the threaded ends of passages 48 and 49 may beaxially disposed.

In order to urge the pressure balance plates 43 and 44 into sealingengagement with the sides of the gear teeth, fluid is supplied to theoutside of the plates. In general, as best seen in FIG. 3, the plate 43is formed at each end on the periphery with a portion of reduced radiusas at 50 to permit uniform distribution of the high pressure outletfluid along a predetermined portion of the gear side of the plate andbehind the plate into an area 52 (FIG. 6) between a pair of sealingrings 54 and 55 in housing member 11, so that the area 52 is subjectedto pressure corresponding generally to that in the outlet chamber. Atopposite sides of the inlet chamber 37, the plate 43 is formed withports 57 which admit fluid to the outside of the plate in areas withincircular O-rings 58 in housing member 11 at pressure intermediate theoutlet pressure and the inlet pressure. The remaining area within ring55 is at approximately inlet pressure due to exposure to inlet passage48. The gear side of the plate 44 is a mirror image of the gear side ofthe plate 43, and the outside of the plate 44 is subjected to fluidpressure similar to that supplied a the outside of plate 43.

In order to provide for lubrication of the opposite ends of the driveshaft and driven shaft in the bearings 34, lubricating fluid is pumpedfrom trapped fluid in a sealed chamber at the zone of intermeshing teethwhere the spaces between teeth decrease in volume, outwardly along theend portions of drive shaft 19, across to the end portions of drivenshaft 21, and back inwardly along the latter to the inlet let chamber.

In order to take lubricating fluid under pressure from the zone ofintermeshing teeth, each of the pressure balanced plate 43 and 44 isformed on the gear side adjacent the drive shaft 19 with a groove as at60 (FIGS. 1, 3 and 7) which extends from the intermeshing teeth inwardlytoward the shaft. The groove 60 terminates at the inner end incommunication with an annular channel as at 61 around the shaft definedradially by the inner surface of the pressure balance plate and theouter surface of the shaft, and defined axially by the inner end of thebearing sleeve and the outer surface of the gear. The annular channel 61communicates with the inner end of longitudinal groove 35 in theadjacent bearing sleeve 34 so that lubricating fluid may flowlongitudinally outwardly along the drive shaft to the bearing recesses28 and 29. In order to seal the high pressure fluid in the annularchannel 61, a groove 62 (FIG. 4) in the outer surface of each pressureplate around the drive shaft includes an O-ring 63 engaging the adjacenthousing member.

In order to communicate the outer end of the bearing recess 28 with theouter end of the bearing recess 24, the end housing member 11 is formedwith a passage 64 which conducts lubricating fluid from the recess 28 tothe recess 24. End housing member includes a passage 65 communicatingthe bearing recess 29 and the bearing recess 25 to permit lubricatingfluid to flow to the latter. Lubricating fluid in the recesses 24 and 25flows inwardly along the driven shaft through the grooves 35 in bearingsleeves 34 to annular channels as at 68 surrounding the driven shaft atopposite sides of the idler gear, like those at 61 on the drive shaft.Each annular channel 68 communicates with the pump inlet chamber 37 bymeans of a recess as at 69 in the face of the pressure plate adjacentthe idler gear extending from annular channel 68 radially outwardly tothe inlet chamber.

The lubricating circuit is described in more detail in our copendingapplication Ser. No. 110,179, filed Jan. 27, l97l.

Considering the pressure plates 43 in more detail, it will be noted onreference to FIG. 2 that the gear includes six teeth in the gear cavity40 between the inlet 37 and the outlet 38, while the gear 18 includesseven teeth in the gear cavity 41 between the inlet 37 and the outlet38. Thus, the length of the arc of rotation of the gears in the gearcavities may be said to correspond approximately to the pitch of sixteeth. According to the present invention, each such arc of rotation isconsidered as involving separate sectors each corresponding respectivelyto the pitch of one tooth. It is contemplated that the pressure in eachsector at the gear side of each pressure plate will be accuratelycounterbalanced in a manner to take into account varying pressuresaround the periphery of the gears within the arc of rotation in eachgear cavity. The force in each sector tending to separate the plate fromthe gear is slightly overbalanced, by about 10 percent for example, in

order to insure that both plates are effectively held in sealedrelationship against the sides of the gear teeth in a manner to avoidsignificant deflection of the plates and in a manner to avoid localizedloads and accompanying wear and torque losses.

As will appear, means is provided to assure that a definitepredetermined primary area at the gear side of each plate is subjectedto outlet pressure. In the preferred construction illustrated, theprimary area includes the intermeshing teeth immediately adjacent theoutlet chamber, the outlet chamber, and approximately four sectors inthe arc of rotation in the gear cavity from the outlet chamber aroundthe gear teeth toward the inlet, corresponding approximately to thepitch of four teeth. The remaining portion in the arc of rotation in thegear cavity of about two sectors corresponding approximately to thepitch of two teeth, from the inlet to each primary area, is exposed tovarying pressure increasing from substantially zero at the inlet tosubstantially outlet pressure at the juncture of the secondary area withthe primary area. At varying speeds, the pressure gradient from theinlet to the primary area varies.

In particular, referring to FIG. 9, a pressure gradient line is drawnfrom the inlet 37 around gear cavity 40 to outlet 38, and a similarpressure gradient line 72 is drawn from inlet 37 around gear cavity 41to outlet 38. The pressure gradient lines 70 and 72 are drawn toindicate operation of the pump at relatively slow speeds, when thepressure rises gradually from the origin 70a, 72a of each line beginningat the edge of the inlet chamber 37 to a maximum value at 70b, 72b. Incontrast, in FIG. 10, pressure gradient lines 74 and 76 are drawn toindicate pump operation at relatively high speeds, when each pressuregradient line beings at origin 74a, 76a, displaced from the inletchamber 37 and rises abruptly to maximum pressure at 74b, 76bcorresponding to the location of 70b, 72b in FIG. 9.

The difference in operation in FIGS. 9 and 10 may be explained asfollows. The pressure drop across a given leakage path varies as thesquare of the fluid velocity. That is, asthe fluid velocity increases,the pressure drop also increases. During operation at high speeds, thegears rotate faster, and the gear tip velocity increases. Since fluidleakage in the example given is in a direction opposite to the movementof the gear tip, the velocity of fluid leaking relative to the gear tipis greater. This results in a higher pressure drop across the tip and aconsequent lower pressure at any given point spaced along the leak pathfrom the high pressure. The problem of varying pressures in the areasdescribed during operation at different speeds results in difficulty inproviding properly balanced seal plates providing optimum results at allspeeds, for the reason that it is not possible to apply a constantpressure balancing force because a constant force will not beproportional to the varying forces tending to separate the plate atvarying speeds. While full pressure is shown to be attained at 70b, 72bin FIG. 9, and at 74b, 76b in FIG. 10, for convenience of demonstratingpressure gradient, it should be understood that in varying pumpconstructions, full pressure may actually be attained at variouspositions along the arc of rotation toward the outlet chamber, in theabsence of special provisions to distribute outlet pressure.

In FIG. 11, a pressure balanced seal plate 43 is illustrated, with apressure pattern superimposed to show the pressures acting on the gearside of the plate tending to separate the plate from the gears in eachof a plurality of sectors in the path of rotation of each of the gears.

In particular, each sector corresponds to the pitch of one tooth andencompasses a tooth centrally located in the sector. For example,considering the upper gear 20, note the sectors 81, 82, 83, 84, 85, 86,87, 88, 89, 90. Similarly, around the lower gear 18 there are sectors91, 92, 93, 94, 95, 96, 97, 98, 99 and 100. In a pump construction ofthe type under consideration, full discharge pressure normally exists inthe outlet chamber 38, in the zone of intermeshing teeth at the side ofthe line of action communicating with the outlet chamber,-and in anumber of the sectors, such as approximately 81, 82, 83, 84 and 85associated with gear and approximately 91, 92, 93, 94 and 95 associatedwith gear 18. Under such circumstances pressure would rise from theinlet chamber 37 gradually through sectors 90, 89, 88, 87 and 86associated with gear 20, and sectors I00, 99, 98, 97 and 96 associatedwith gear 18. The actual location where full pressure is attained mayvary under various operating conditions.

In the present construction, provision is made for defining a clearlydelineated area in which discharge pressure exists. In particular, therecess 50 in the periphery of the seal plate at each end extendsapproximately from the sector 84 to the sector 87 associated with gear20, and from the sector 94 to the sector 96 associated with the gear 18.The recesses 50 assure distribution of discharge pressure to the end ofthe recess nearest the inlet and result in definition of a primarypressure area approximately in the shape of an E (FIG. 11) extendingfrom the zone of intermeshing teeth at the outlet chamber and aroundboth gears. The middle terminus of the primary pressure area isdesignated at Y and each end terminus is designated atZ. Since only alimited portion, if any, of sectors 88 and 97 are included, forpractical purposes the primary area ends approximately at the sector 87and approximately at the sector 96.

As shown in FIG. 12, full outlet pressure exists in the spaces betweenthe gear teeth in the primary area as represented by the crosshatchingat 104. At the inner periphery of the seal plate, the pressure issubstantially zero as indicated by the crosshatching at 106. Alongsidethe gear and the. gear teeth, the pressure varies gradually from zero at106 to full outlet pressure at 104. In FIG. 12, the variation is shownin four intermediate steps, I07, I08, 109 and 110, for purposes ofillustration. If the full outlet pressure is 3500 psi, the variation ineach step is approximately 700 psi. FIG. 12 demonstrates the manner inwhich the forces in each sector in the primary area tending to separatethe plate from the gears may be accurately determined in order toprovide an appropriate overbalancing force to adequately hold the platein sealing relationshipwith the gears while at the same time avoidingapplication of undue forces tending to distort the plate and create wearor leakage.

In FIG. 11, each area leading from the zone of intermeshing teeththrough the inlet around gear 20 and around gear 18 to the primary areais referred to as a secondary area which is subjected to varyingpressure as described in connection with FIGS. 9 and 10.

Referring now to FIG. 13, as well as FIG. 6, it will be noted that thesealing ring 55 in the end housing member defines the inner perimeter ofa pressure balance area 1 14 on the remote side of plate 43 opposing theprimary force tending to separate the plate. From the inner perimeterdefined by the ring 55, the pressure balance area 114 extends outwardlyto the outer edge of the plate. The pressure balance area correspondsapproximately to the primary area on the gear side of the plate and hasa generally 3-shaped configuration (FIG. 13) encompassing the zone ofintermeshing teeth as at 116, the outlet chamber 38, and a plurality ofsectors around each of the gears. The primary pressure balance areaterminates at each end at a position spaced from the beginning of thegear cavity a distance corresponding to the pitch of one and a half totwo teeth, which assures adequate sealing of the inlet chamber from eachrecess 50. The outer perimeter of the primary pressure balance area 114lies within the chamber 52 (FIG. 6) which has an outer perimeter definedby the sealing member 54 in the end housing member. It will beunderstood that fluid at outlet pressure is supplied to the primarypressure balance areas 114 by virtue of the recesses 50 at opposite endsof the plate and by virtue of limited clearance along the periphery ofthe plate at the outlet side of the pump due to shifting toward theinlet which results from discharge pressure.

Opposed to each of the secondary areas having pressure tending toseparate the plate from the gears are secondary pressure balance areason the remote side of each plate lying within the circular O-ring seals58 (FIG. 6) in the end housing member. Referring to FIG. 6, the O-rings58 are located approximately centrally between the sealing member 55 andthe edge of inlet 48. Within such space limitations the areas 120 aremade as large as practicable. Fluid at appropriate pressure to providethe necessary counterbalance force is supplied to each chamber 120through the aperture 57 (FIGS. 3 and 4) located centrally relative tochamber 120. In order to utilize pressures at appropriate values in thepressure gradient, the aperture is angularly elongated at the gear sideof the plate as illustrated by the groove at 57a (FIG. 3).

More particularly, as the leading edge of a gear tooth passes the grooveor slot 57a, the pressure increases from the beginning of the slotadjacent the inlet chamber 37 to the end of the slot remote from theinlet chamber. It is desirable to utilize the pressure at the end of theslot remote from the inlet chamber to provide adequate counter balanceforces. However, as soon as the trailing edge of the gear tooth passesthe pressure balance chamber 120, the pressure at the gear side of theplate subsides, and the fluid trapped in chamber 120 would unduly biasthe wear plate toward passes the near end of the slot. The length of theslot is slightly less than the thickness ofa tooth.

In order to assure adequate seal along the periphery of each pressureplate between the inlet chamber and the end of recess 50, the plate isformed of appropriate material such as an aluminum alloy with a land 125(FIGS. 3, 4 and 8) which is formed with a slight bevel on the order ofto 3')? as best seen in FIG. 8. ln use, when the pump develops highpressure in the outlet chamber, such pressure acts on the periphery ofthe gear plate adjacent the outlet chamber and tends to force the gearplate laterally toward the inlet chamber, as a result of which thebeveled edge 125 is forced against the surrounding gear cavity wall inthe central spacer plate 12. The force is adequate to flatten thebeveled edge as shown at 1250 (FIG. 8) in a manner such that the edgemay conform with the gear cavity wall and any irregularities therein toprovide a tight seal between the inlet chamber and the recess 50. Inthis way, the fluid at high pressure in the primary pressure area, inthe recess 50, and in the pressure balance area 114, is separated fromthe varying pressure along the gradient from the inlet chamber to theend of recess 50.

In order to simplify manufacture, the lands at the periphery of theplate adjacent the outlet are beveled also.

The curves in FIGS. 14 and 15 demonstrate the high degree of volumetricand overall efficiency provided in a construction embodying the presentinvention.

We claim:

I. A high pressure rotary gear pump, comprising:

a. a housing having a pair of gear cavities,

b. a pair of gears in the cavities having gear teeth intermeshing,

c. an inlet chamber at one side of the intermeshing teeth,

an outlet chamber at the other side of the intermeshing teeth,

. a pair of shafts respectively carrying said gears,

a floating seal plate against one side of the gears having a centralportion in the inlet chamber exposed to inlet pressure,

means defining a primary area exposed to outlet pressure on the gearside of the seal plate extending from the intermeshing teeth adjacentthe outlet chamber and around the gears at least half way toward theinlet chamber applying a primary force tending to separate the platefrom the gears,

means defining a pressure balance area on the remote side of the plateopposed to said primary area and of proportions sufficient to overcomethe primary force and hold the plate against the gears when such balancearea is exposed to outlet pressure,

. means for supplying outlet pressure to the primary pressure balancearea,

j. means defining secondary areas exposed to varying pressure on thegear side of the plate increasing from the intermeshing teeth adjacentthe inlet chamber around each gear toward the outlet chamber to theprimary area applying secondary forces tending to separate the platefrom the gears,

k. means defining a pressure balance area on the remote side of theplate opposed to each secondary area and of predetermined proportionssufficient to overcome the secondary force when such balance area issubjected to predetermined pressure, and l l. means for supplyingpressure at a predetermined value intermediate inlet pressure and outletpressure from the gear side of the plates to the secondary balanceareas.

2. A pump as defined in claim 1, wherein the means defining the primaryand secondary areas on the gear side of the plate includes a recess inthe periphery of the plate extending around the plate from a positionnormally at outlet pressure to a position normally less than outletpressure but subjected to outlet pressure by the recess, and

means on the periphery of the plate engaging the housing and sealing thesecondary area from the primary area.

3. A pump as defined in claim 1, wherein the means defining the primarypressure balance area includes sealing members between the remote sideof the plate and the housing, and

the means defining each secondary pressure balance area includes asealing ring between the remote side of the plate and the housingcommunicating with the gear side of the plate between the inlet and theprimary area.

4. A high pressure rotary gear pump, comprising: a. a housing having apair of generally cylindrical gear cavities intersecting centrally ofthe housing, b. a pair of external gears in the cavities having gearteeth intermeshing at a zone centrally of the housing,

c. an inlet chamber at one side of the zone of intermeshing teeth wherethe spaces between intermeshing teeth increase in volume,

(1. an outlet chamber at the other side of the zone of intermeshingteeth where the spaces between the intermeshing teeth decrease involume,

e. a pair of shafts respectively carrying said gears fixed thereon andhaving opposite ends mounted in the housing,

f. a pair of generally 8-shaped seal plates around the shafts againstopposite sides of the gears,

g. a recess in the periphery of each plate at each end defining aprimary area exposed to outlet pressure on the gear side of each sealplate from the zone of intermeshing teeth adjacent the outlet chamberand around the gears more than half way toward the inlet chamberapplying primary force tending to separate the plate from the gears,

h. means defining a pressure balance area on the remote side of eachplate opposed to said primary area and of proportions sufficient toovercome the primary force and hold the plate against the gears whensuch balance area is exposed to outlet pressure, l

. said recess supplying outlet pressure to the primary pressure balancearea,

j. a land on the periphery of each plate between the inlet and eachrecess sealing each recess from the inlet and defining secondary areassubject to varying pressure on the gear side of each plate increasingfrom the zone of intermeshing teeth adjacent the inlet chamber aroundthe gears toward the outadjacent the inlet is beveled to deform in usein the pump when subjected to high pressure.

let chamber to the primary area applying a secondary force tending toseparate the plate from the gears,

k. means defining a pressure balance area on the remote side of eachplate opposed to each secondary area and of predetermined proportionssufficient to overcome the secondary force when such balance area issubject to predetermined pressure, and

I. an aperture in the plate intermediate the ends of each secondary areafor supplying pressure at a predetermined value intermediate inletpressure and outlet pressure from the gear side of the plates to thesecondary balance areas. I

5. A pump as defined in claim 4 wherein the means 6. A pump as definedin claim 4 wherein the means defining each secondary pressure balancearea includes a circular O-ring in the housing at the remote side ofeach plate.

7. A pump as defined in claim 4 wherein the length of each landcorresponds approximately to the pitch of one and a half to two teeth.

8. A pump as defined in claim 4 wherein each land 9. A high pressurerotary gear pump, comprising,

a. a housing having a pair of generally cylindrical gear cavitiesintersecting centrally of the housing, b. a pair of external spur gearsin the cavities having gear teeth intermeshing at a zone centrally ofthe housing,

c. an inlet chamber at one side of the zone of intermeshing teeth wherethe spaces between intermeshing teeth increase in volume,

(1. an outlet chamber at the other side of the zone of intermeshingteeth where the spaces between the intermeshing teeth decrease involume,

e. a pair of shafts respectively carrying said gears fixed thereon andhaving opposite ends mounted in the housing,

f. a pair of thin generally 8-shaped floating seal plates around theshafts against opposite sides of the gears forming with the intermeshingteeth a seal between the inlet and outlet and sealing the gear teethrotating from the inlet chamber to the outlet chamber,

g. a primary area exposed to outlet pressure on the gear side of eachseal plate from the zone of intermeshing teeth adjacent the outletchamber and aroundthe gears more than half way toward the inlet/chamberapplying primary force tending to separate the plate from the gears,

h. a sealing ring in the housing at the remote side of each platedefining the inner perimeter of a pressure balance area on the remoteside of each plate opposed to said primary area and of proportionssufficient to slightly overcome the primary force and hold the plateagainst the gears when such balance area is exposed to outlet pressure,I. a recess in the periphery of each plate at each end thereof extendingfrom a position normally at outlet pressure around the periphery of theplate to a position normally at less than outlet pressure to define theprimary area and supply fluid at outlet pressure to the primary pressurebalance area,

j. a land on the periphery of each plate between the inlet and eachrecess engaging the housing and sealing the recess from the inletthereby defining secondary areas subject to varying pressure on the gearside of each plate increasing from the zone of intermeshing teethadjacent the inlet chamber around the gears toward the outlet chamber tothe primary area applying a secondary force tending to separate theplate from the gears,

k. an O-ring in the housing at the remote side of each plate defining apressure balance area on the remote side of each plate opposed to eachsecondary area and of predetermined proportions sufficient to overcomethe secondary force when such balance area is subject to predeterminedpressure, and

1. an aperture in the plate intermediate the ends of each secondary areafor supplying pressure at a predetermined value intermediate inletpressure and outlet pressure from the gear side of the plates to thesecondary balance areas.

10. A pump as defined in claim 9 wherein the sealing ring defining theinner perimeter of the primary pressure balance area is arrangedapproximately in a 3- shaped pattern providing approximately a 3-shapedpressure balance area encompassing the zone of intermeshing teeth andthe outlet, and each O-ring defining a secondary pressure balance areais circular.

11. A pump as defined in claim 9 wherein the length of each land isapproximately the pitch of one and a halt" to two teeth, and each landis beveled to deform in use in the pump when subjected to high pressure,thereby to conform with the surrounding housing and provide an effectiveseal between the inlet and the primary area.

12. A pump as defined in claim 1, wherein the means for supplyingpressure fluid to each secondary balance area includes a port throughthe seal plate centrally of the secondary balance area, and an inletgroove in the face of the plate adjacent the gears communicating withthe port and elongated relative to the port in the direction of geartooth movement.

13. A pump as defined in claim 12, wherein the end of said groove remotefrom the inlet chamber is located to provide suitable pressure forappropriate counterbalance forces as the leading edge of a tooth passes,and the endof the groove adjacent the inlet chamber is located torelieve pressure in the secondary balance area when the trailing edge ofa tooth is opposite the secondary balance area.

14. A pump as defined in claim 13, wherein the length of the groove isslightly less than the thickness of a tooth, and the trailing end vofthe groove is aligned with the port.

1. A high pressure rotary gear pump, comprising: a. a housing having apair of gear cavities, b. a pair of gears in the cavities having gearteeth intermeshing, c. an inlet chamber at one side of the intermeshingteeth, d. an outlet chamber at the other side of the intermeshing teeth,e. a pair of shafts respectively carrying said gears, f. a floating sealplate against one side of the gears having a central portion in theinlet chamber exposed to inlet pressure, g. means defining a primaryarea exposed to outlet pressure on the gear side of the seal plateextending from the intermeshing teeth adjacent the outlet chamber andaround the gears at least half way toward the inlet chamber applying aprimary force tending to separate the plate from the gears, h. meansdefining a pressure balance area on the remote side of the plate opposedto said primary area and of proportions sufficient to overcome theprimary force and hold the plate against the gears when such balancearea is exposed to outlet pressure, i. means for supplying outletpressure to the primary pressure balance area, j. means definingsecondary areas exposed to varying pressure on the gear side of theplate increasing from the intermeshing teeth adjacent the inlet chamberaround each gear toward the outlet chamber to the primary area applyingsecondary forces tending to separate the plate from the gears, k. meansdefining a pressure balance area on the remote side of the plate opposedto each secondary area and of predetermined proportions sufficient toovercome the secondary force when such balance area is subjected topredetermined pressure, and l. means for supplying pressure at apredetermined value intermediate inlet pressure and outlet pressure fromthe gear side of the plates to the secondary balance areas.
 1. A highpressure rotary gear pump, comprising: a. a housing having a pair ofgear cavities, b. a pair of gears in the cavities having gear teethintermeshing, c. an inlet chamber at one side of the intermeshing teeth,d. an outlet chamber at the other side of the intermeshing teeth, e. apair of shafts respectively carrying said gears, f. a floating sealplate against one side of the gears having a central portion in theinlet chamber exposed to inlet pressure, g. means defining a primaryarea exposed to outlet pressure on the gear side of the seal plateextending from the intermeshing teeth adjacent the outlet chamber andaround the gears at least half way toward the inlet chamber applying aprimary force tending to separate the plate from the gears, h. meansdefining a pressure balance area on the remote side of the plate opposedto said primary area and of proportions sufficient to overcome theprimary force and hold the plate against the gears when such balancearea is exposed to outlet pressure, i. means for supplying outletpressure to the primary pressure balance area, j. means definingsecondary areas exposed to varying pressure on the gear side of theplate increasing from the intermeshing teeth adjacent the inlet chamberaround each gear toward the outlet chamber to the primary area applyingsecondary forces tending to separate the plate from the gears, k. meansdefining a pressure balance area on the remote side of the plate opposedto each secondary area and of predetermined proportions sufficient toovercome the secondary force when such balance area is subjected topredetermined pressure, and l. means for supplying pressure at apredetermined value intermediate inlet pressure and outlet pressure fromthe gear side of the plates to the secondary balance areas.
 2. A pump asdefined in claim 1, wherein the means defining the primary and secondaryareas on the gear side of the plate includes a recess in the peripheryof the plate extending around the plate from a position normally atoutlet pressure to a position normally less than outlet pressure butsubjected to outlet pressure by the recess, and means on the peripheryof the plate engaging the housing and sealing the secondary area fromthe primary area.
 3. A pump as defined in claim 1, wherein the meansdefining the primary pressure balance area includes sealing membersbetween the remote side of the plate and the housing, and the meansdefining each secondary pressure balance area includes a sealing ringbetween the remote side of the plate and the housing communicating withthe gear side of the plate between the inlet and the primary area.
 4. Ahigh pressure rotary gear pump, comprising: a. a housing having a pairof generally cylindrical gear cavities intersecting centrally of thehousing, b. a pair of external gears in the cavities having gear teethintermeshing at a zone centrally of the housing, c. an inlet chamber atone side of the zone of intermeshing teeth where the spaces betweenintermeshing teeth increase in volume, d. an outlet chamber at the otherside of the zone of intermeshing teeth where the spaces between theintermeshing teeth decrease in volume, e. a pair of shafts respectivelycarrying said gears fixed thereon and having opposite ends mounted inthe housing, f. a pair of generally 8-shaped seal plates around theshafts against opposite sides of the gears, g. a recess in the peripheryof each plate at each end defining a primary area exposed to outletpressure on the gear side of each seal plate from the zone ofintermeshing teeth adjacent the outlet chamber and around the gears morethan half way toward the inlet chamber applying primary force tending toseparate the plate from the gears, h. means defining a pressure balancearea on the remote side of each plate opposed to said primary area andof proportions sufficient to overcome the primary force and hold theplate against the gears when such balance area is exposed to outletpressure, i. said recess supplying outlet pressure to the primarypressure balance area, j. a land on the periphery of each plate betweenthe inlet and each recess sealing each recess from the inlet anddefining secondary areas subject to varying pressure on the gear side ofeach plate increasing from the zone of intermeshing teeth adjacent theinlet chamber around the gears toward the outlet chamber to the primaryarea applying a secondary force tending to separate the plate from thegears, k. means defining a pressure balance area on the remote side ofeach plate opposed to each secondary area and of predeterminedproportions sufficient to overcome the secondary force when such balancearea is subject to predetermined pressure, and l. an aperture in theplate intermediate the ends of each secondary area for supplyingpressure at a predetermined value intermediate inlet pressurE and outletpressure from the gear side of the plates to the secondary balanceareas.
 5. A pump as defined in claim 4 wherein the means defining eachprimary pressure balance area includes a sealing ring in the housing atthe remote side of each plate in approximately a 3-shaped pattern at theinner perimeter of the primary pressure balance area providingapproximately a 3-shaped area encompassing the zone of intermeshingteeth and the outlet.
 6. A pump as defined in claim 4 wherein the meansdefining each secondary pressure balance area includes a circular O-ringin the housing at the remote side of each plate.
 7. A pump as defined inclaim 4 wherein the length of each land corresponds approximately to thepitch of one and a half to two teeth.
 8. A pump as defined in claim 4wherein each land adjacent the inlet is beveled to deform in use in thepump when subjected to high pressure.
 9. A high pressure rotary gearpump, comprising, a. a housing having a pair of generally cylindricalgear cavities intersecting centrally of the housing, b. a pair ofexternal spur gears in the cavities having gear teeth intermeshing at azone centrally of the housing, c. an inlet chamber at one side of thezone of intermeshing teeth where the spaces between intermeshing teethincrease in volume, d. an outlet chamber at the other side of the zoneof intermeshing teeth where the spaces between the intermeshing teethdecrease in volume, e. a pair of shafts respectively carrying said gearsfixed thereon and having opposite ends mounted in the housing, f. a pairof thin generally 8-shaped floating seal plates around the shaftsagainst opposite sides of the gears forming with the intermeshing teetha seal between the inlet and outlet and sealing the gear teeth rotatingfrom the inlet chamber to the outlet chamber, g. a primary area exposedto outlet pressure on the gear side of each seal plate from the zone ofintermeshing teeth adjacent the outlet chamber and around the gears morethan half way toward the inlet chamber applying primary force tending toseparate the plate from the gears, h. a sealing ring in the housing atthe remote side of each plate defining the inner perimeter of a pressurebalance area on the remote side of each plate opposed to said primaryarea and of proportions sufficient to slightly overcome the primaryforce and hold the plate against the gears when such balance area isexposed to outlet pressure, i. a recess in the periphery of each plateat each end thereof extending from a position normally at outletpressure around the periphery of the plate to a position normally atless than outlet pressure to define the primary area and supply fluid atoutlet pressure to the primary pressure balance area, j. a land on theperiphery of each plate between the inlet and each recess engaging thehousing and sealing the recess from the inlet thereby defining secondaryareas subject to varying pressure on the gear side of each plateincreasing from the zone of intermeshing teeth adjacent the inletchamber around the gears toward the outlet chamber to the primary areaapplying a secondary force tending to separate the plate from the gears,k. an O-ring in the housing at the remote side of each plate defining apressure balance area on the remote side of each plate opposed to eachsecondary area and of predetermined proportions sufficient to overcomethe secondary force when such balance area is subject to predeterminedpressure, and l. an aperture in the plate intermediate the ends of eachsecondary area for supplying pressure at a predetermined valueintermediate inlet pressure and outlet pressure from the gear side ofthe plates to the secondary balance areas.
 10. A pump as defined inclaim 9 wherein the sealing ring defining the inner perimeter of theprimary pressure balance area is arranged approximately in a 3-shapedpattern providing approximately a 3-shaped pressure balance areaenCompassing the zone of intermeshing teeth and the outlet, and eachO-ring defining a secondary pressure balance area is circular.
 11. Apump as defined in claim 9 wherein the length of each land isapproximately the pitch of one and a half to two teeth, and each land isbeveled to deform in use in the pump when subjected to high pressure,thereby to conform with the surrounding housing and provide an effectiveseal between the inlet and the primary area.
 12. A pump as defined inclaim 1, wherein the means for supplying pressure fluid to eachsecondary balance area includes a port through the seal plate centrallyof the secondary balance area, and an inlet groove in the face of theplate adjacent the gears communicating with the port and elongatedrelative to the port in the direction of gear tooth movement.
 13. A pumpas defined in claim 12, wherein the end of said groove remote from theinlet chamber is located to provide suitable pressure for appropriatecounterbalance forces as the leading edge of a tooth passes, and the endof the groove adjacent the inlet chamber is located to relieve pressurein the secondary balance area when the trailing edge of a tooth isopposite the secondary balance area.